Drain the oil, clean out the air box of any water, drain the carb(small screw on bottom of float bowl, drain the clutch cover, fill with oil and crank her up. If it starts don't rev it up just idle for 5min then drain oil again. Repeat until oil is clean.
Something I found out the hard way on my 700H1. there is a seal behind the primary that may need changed if it starts to leak. I had my clutch full of sand, mud, etc and it caused it to leak there after. Just something to look at
Like others stated, drain oil, fill with diesel. Disconnect spark plug wire and remove spark plug. Spin engine a few seconds (5-6 seconds)the first time, drain dirty diesel, then do it again until diesel comes out clean (usually 3 to 5 times). If water got in the cylinder its good to disconnect the header pipe and run diesel thru the cylinder (pour down spark plug hole).